Tutorials covering the tools that developers use every day — version control, editors, build systems, package managers, containers, and the command-line utilities that make work faster. Each chapter is standalone, built around real examples and verified commands.
A Docker image is not a single file. It is a manifest that references a configuration and an ordered list of layers, and each layer is stored as a content-addressed blob. This architecture is what makes images distributable, shareable, and verifiable. When you pull an image, Docker does not download a monolithic tarball; it fetches…
npm lifecycle scripts are hooks that run automatically at specific points in a package’s lifecycle—during install, pack, publish, or when a user-defined script is invoked. The pre and post prefixes are the general mechanism: any script named prefoo runs before foo, and postfoo runs after it . The special scripts prepare, prepublishOnly, and the deprecated…
Docker images are portable only when they are stored in a registry. The local daemon holds images built or pulled on a machine, but those images are not available to other machines, to CI runners, or to a Kubernetes cluster until they are pushed to a registry. Docker Hub is the default public registry, and…
Environment variables are the mechanism by which npm scripts receive configuration that varies by machine, by environment, or by deployment target. A script that reads process.env.NODE_ENV or process.env.API_URL is not hardcoded to a single setup; it adapts based on what the surrounding shell or .env file provides. The complication is that setting environment variables in…
A Dockerfile is a text file with instructions that the image builder reads in order. Each instruction creates a layer, and the final layer stack becomes the image. The three instructions that most define an image’s behavior are FROM, which sets the base, RUN, which executes commands during the build, and CMD and ENTRYPOINT, which…
Package maintenance is not a single command but a cycle. npm update advances dependencies within the semver ranges declared in package.json. npm audit inspects the dependency tree for known vulnerabilities and optionally applies fixes. npm uninstall removes a package and cleans up every reference to it. Each command modifies a different artifact—node_modules, package-lock.json, or package.json—and…
CMD and ENTRYPOINT are the two Dockerfile instructions that determine what a container runs. They are similar enough to be confused and different enough that the confusion causes real problems: containers that ignore their configuration, applications that never receive SIGTERM, and images that cannot be used as a base for anything else. The confusion is…
An npm account is the credential that separates a consumer of packages from a publisher. Creating one takes minutes, but the account that can actually publish is a different thing from the account that was just created. Publishing to the public registry requires two gates to be cleared: email verification and two-factor authentication . The…
COPY and ADD are the two Dockerfile instructions that bring files from the build context into the image. They look interchangeable, and for the simple case of copying a local file they behave identically. The difference is that ADD does two extra things: it auto-extracts local tar archives and it can fetch remote URLs. Those…
A published package is consumed by many different resolvers: Node.js in CommonJS mode, Node.js in ESM mode, TypeScript with legacy module resolution, TypeScript with modern bundler or node16 resolution, and bundlers like Vite and Webpack. Each resolver looks at package.json differently. The four fields that determine whether a package works across all of them are…